feat. rebuild service in Go

Rebuild the Gitea Codex review bot from the product contract with a Go HTTP service, durable SQL queue, typed Gitea client, isolated runner, and deployment updates.

Co-Authored-By: Claude <noreply@anthropic.com>

internal/webhook/webhook_test.go

@@ -0,0 +1,39 @@
+package webhook
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"testing"
+)
+
+func TestVerifySignatureUsesRawBodyAndPrefix(t *testing.T) {
+	body := []byte(`{"ok":true}`)
+	mac := hmac.New(sha256.New, []byte("secret"))
+	_, _ = mac.Write(body)
+	signature := hex.EncodeToString(mac.Sum(nil))
+	if !VerifySignature(body, "secret", "sha256="+signature) {
+		t.Fatal("valid signature was rejected")
+	}
+	if VerifySignature([]byte(`{"ok":false}`), "secret", signature) {
+		t.Fatal("changed body was accepted")
+	}
+	if VerifySignature(body, "wrong", signature) {
+		t.Fatal("wrong secret was accepted")
+	}
+}
+
+func TestParseEvents(t *testing.T) {
+	body := []byte(`{"repository":{"full_name":"acme/repo"},"sender":{"username":"alice"},"comment":{"id":11,"body":"@codex review"},"issue":{"number":9,"pull_request":{"url":"x"}},"pull_request":{"head":{"sha":"abc"}}}`)
+	event, err := ParseEvent("issue_comment", "delivery-1", body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if event.Repo != "acme/repo" || event.PRNumber != 9 || event.HeadSHA != "abc" || event.CommentID != 11 {
+		t.Fatalf("unexpected event: %#v", event)
+	}
+	bad := []byte(`{"repository":{"full_name":"acme/repo"},"comment":{"id":1},"issue":{"number":9}}`)
+	if _, err := ParseEvent("issue_comment", "", bad); err == nil {
+		t.Fatal("non-PR issue comment was accepted")
+	}
+}